Seasonal productivity drives aggregations of killer whales and other cetaceans over submarine canyons of the Bremer Sub-Basin, south-western Australia

Cetaceans are iconic predators that serve as important indicators of marine ecosystem health. The Bremer Sub-Basin, south-western Australia, supports a diverse cetacean community including the largest documented aggregation of killer whales (Orcinus orca) in Australian waters. Knowledge of cetacean...

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Bibliographic Details
Published in:Australian Mammalogy
Main Authors: Salgado Kent, Chandra, Bouchet, Phil, Wellard, Rebecca, Parnum, Iain, Fouda, Leila, Erbe, Christine
Format: Article in Journal/Newspaper
Language:English
Published: CSIRO PUBLISHING 2020
Subjects:
Science & Technology
Life Sciences & Biomedicine
Zoology
generalised estimating equations
habitat modelling
submarine canyons
temporal autocorrelation
whale watching
ESTIMATING EQUATIONS
FORAGING BEHAVIOR
HABITAT
MODELS
POPULATION
ABUNDANCE
PREFERENCES
SELECTION
POD
BAY
Killer Whale
Orca
Orcinus orca
Killer whale
Online Access:https://hdl.handle.net/20.500.11937/80261
https://doi.org/10.1071/AM19058
Description
Summary:Cetaceans are iconic predators that serve as important indicators of marine ecosystem health. The Bremer Sub-Basin, south-western Australia, supports a diverse cetacean community including the largest documented aggregation of killer whales (Orcinus orca) in Australian waters. Knowledge of cetacean distributions is critical for managing the area’s thriving ecotourism industry, yet is largely sporadic. Here we combined aerial with opportunistic ship-borne surveys during 2015–2017 to describe the occurrence of multiple cetacean species on a regional scale. We used generalised estimating equations to model variation in killer whale relative density as a function of both static and dynamic covariates, including seabed depth, slope, and chlorophyll a concentration, while accounting for autocorrelation. Encountered cetacean groups included: killer (n ¼ 177), sperm (n ¼ 69), long-finned pilot (n ¼ 29), false killer (n ¼ 2), and straptoothed beaked (n ¼ 1) whales, as well as bottlenose (n ¼ 12) and common (n ¼ 5) dolphins. Killer whale numbers peaked in areas of low temperatures and high primary productivity, likely due to seasonal upwelling of nutrient-rich waters supporting high prey biomass. The best predictive model highlighted potential killer whale ‘hotspots’ in the Henry, Hood, Pallinup and Bremer Canyons. This study demonstrates the value of abundance data from platforms of opportunity for marine planning and wildlife management in the open ocean.

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